The present invention relates generally to mechanisms for protecting mechanical drive components from overloads, and more particularly relates to a seal hub for use with a shear device coupled between components of an agricultural disc mower that protects the various components of the mower in the event a cutterhead strikes an object and creates an overload condition in the driveline.
Typical disc cutterbars used in agriculture include an elongated housing containing a train of meshed idler and drive spur gears, or a main power shaft or series of power shafts coupled by respective bevel gear sets, for delivering power to respective drive shafts for cutterheads spaced along the length of the cutterbar. The cutterheads each comprise a cutting disc including diametrically opposed cutting blades (though configurations with three or more blades are known) and having a hub coupled to an upper end of a drive shaft, the lower end of the drive shaft carrying a spur gear in the case where a train of meshed spur gears is used for delivering power, and carrying a bevel gear of a given one of the bevel gear sets in the case where a main power shaft is used. In either case, as would be expected, bearings are used to support the various shafts. The cutterheads are rotated at a relatively fast speed making the drive components, such as gears, bearings, and shafts vulnerable to damage in the event that the unit strikes a foreign object. For background information on the structure and operation of some typical disc cutterbars, reference is made to U.S. Pat. No. 4,815,262, issued to Koch, the descriptive portions thereof being incorporated herein in full by reference.
In order to minimize the extent of such possible damage to the drive components, it is known to incorporate a shear device somewhere in the drive of each unit which will “fail” upon a predetermined overload being imposed on the device. As used herein with reference to shear devices, the terms “fail” or “failing” are intended to cover the actual function of such devices, i.e., shearing, fracturing, breaking and the like.
One known type of shear mechanism employs shearable splines engaged on a splined shaft. The shear device is in the form of either a collar or clamping member having internal frangible splines received on a splined end of the drive shaft. An overload situation preferably causes the frangible splines in the shear device to shear and the continuing transfer of rotational power to cease. Following an overload situation, fragments from frangible splines may be dispersed in the cavity surround the splined shaft and shear device. As the shear device is typically positioned in close proximity to disc cutter bearings and drive gears, the potential for introducing metallic fragments into the disc cutter drive and sealing components is great.
It would be advantageous to have a sealing device for use with a frangible element driveline shock protection device to reduce or eliminate the potential for contamination by metallic fragments that overcomes the above problems and limitations. Further advantages would be realized by a seal device that would allow replacement of the fractured shock protection device without risking entry of fragments into the disc cutter drive.